U.S. Severe Weather Forecast (Coup d'œil sur la convection)

Aujourd'hui
Demain
Day Three

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Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0150 PM CST sun Mar 01 2015 


Valid 012000z - 021200z 


..no severe thunderstorm areas forecast... 


... 
widely scattered thunderstorms will occur mainly today over parts of 
central and Southern California...over southeast Texas and the lower 
Mississippi Valley...and over central Florida. 


No changes are made to the outlook for this issuance. 


.Broyles.. 03/01/2015 


Previous discussion... /issued 1029 am CST sun Mar 01 2015/ 


..synoptic setup... 
Split flow will persist across the lower 48...downstream from 
amplified east Pacific Ridge. Elongated California/far east Pacific low expected 
to edge only slowly south-southeast until late in the period...when system 
should turn and accelerate NE in response to shortwave impulse now 
over the British Columbia CST. East of the California system...zonal flow will prevail from 
the plains to the east CST. Heights should rebound over the Southern Plains 
later in the period as northern stream disturbance now over the northern plains 
continues east to the lower Great Lakes. 


With the exception of central/southern Florida and far southeast Texas/parts of 
la...shallow Arctic or modified polar air will linger over most 
areas east of The Rockies. Slightly elevated warm air advection/moisture transport 
regime will persist over East Texas and the lower MS valley...but will be 
increasingly undercut with time by southeastward progression of shallow 
cool-air surge now evolving over the Southern Plains. Similarly in central 
Florida...overall thermal advection will be minimal. While daytime mixing 
may permit a slight northward drift to old west-east front stalled over the 
central part of the state...overall conditions should remain largely 
unchanged. 


..cntrl Florida today... 
Moderate daytime heating of maritime tropical air with moist 
adiabatic temperature profiles may yield scattered afternoon showers/thunderstorms 
over parts of central and perhaps southern Florida. Weak cin and absence of 
significant thermal advection across region suggest that activity 
will require some degree of convergence to be realized...with the 
latter likely being maximized near intersection of old west-east front and 
sea-breeze boundaries over the west central part of the state. While precipitable water 
will remain fairly high...weak shear will limit potential for any 
sustained wind threat. 


..cntrl/Southern California today/tngt... 
The area of coldest air aloft/strongest forcing for ascent with upper 
low/trough will remain off the Southern California CST today as upper low pivots 
slowly south-southeast across region. But moderate to strong surface heating beneath 
associated trough axis...and terrain circulations...should support 
widely scattered afternoon showers/storms over parts of central/Southern California. Although 
small hail could accompany some cells...buoyancy will be weak 
/around 250 j/kg MUCAPE/ and deep shear modest given proximity of 
trough. Thus...sustained severe weather is not expected. 


..E Texas/lower MS valley through early Monday... 
Other than a slight weakening and aforementioned undercutting... 
little overall change is expected in elevated warm air advection/moisture transport 
regime now in progress over East Texas and the lower MS valley. Coupled with 
absence of middle- and upper-level forcing for ascent...the prospects for 
strong to severe convection appear minimal. Nevertheless...sporadic 
clusters of slightly elevated thunderstorms likely will persist and spread 
slightly northeastward with time. 

Mesoscale Discussion


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Mesoscale discussion 0110 
National Weather Service Storm Prediction Center Norman OK 
1257 PM CST sun Mar 01 2015 


Areas affected...northeast coast 


Concerning...winter mixed precipitation 


Valid 011857z - 020000z 


Summary...snowfall rates across portions of southern New England and 
Long Island are expected to increase over the next several hours 
with snowfall rates occasionally exceeding 1 inch per hour. A 
transition from snow to freezing rain is expected across 
Delaware...cntrl/srn New Jersey...and far eastern PA. Freezing rain rates may top 0.05 
inch per hour with total accumulations around 0.10 to 0.20 
inch...locally higher...possible. 


Discussion...surface observations and regional radar imagery 
indicate areas of freezing rain across NE Maryland with moderate 
snow northeastward across New Jersey...Long Island...and into southern New England. 
Overall upper pattern is expected to change little over the next 
several hours -- aside from a general increase in middle/upper wind 
speeds -- with persistent middle-level warm air advection favoring a continuation of 
precipitation across the region amidst gradually warming middle-level 
temperatures. As such...a transition from snow/sleet to mostly 
freezing rain is expected over Delaware and most of New Jersey within the next 
hour or two. Once this transition occurs...freezing rain rates may 
top 0.05 inch per hour. Given the expected persistence of the 
precipitation...the potential for significant ice accumulations -- 
at or above 0.25 inch -- is possible...although accumulations closer 
to 0.15 inch appear more likely. 


Farther north /Long Island...southern New England/...snowfall rates are 
expected to gradually increase as the middle-level flow and resultant 
warm air advection increase. Snowfall rates will generally be less than one inch 
per hour but the potential exist rates in excess of one inch per 
hour within any bands that set up. 


.Mosier/corfidi.. 03/01/2015 


..please see www.Spc.NOAA.Gov for graphic product... 


Attention...WFO...box...okx...aly...phi...bgm...ctp...lwx... 


Latitude...Lon 40927194 40417364 39627416 38577533 39007614 39837655 
40747575 41357477 42047257 41927052 40927194